In recent years due to market acceptance of products having less gold content (ie. lighter weight than solid gold jewelry), the U.S. jewelry industry has gone through many changes. The latest trend is using the combination of silver and gold in making the jewelry objects, thus achieving a less expensive product by virtue of the fact that gold is priced about 70 times more than silver. Hollow wire or tubing with thin walls has been used for over 50 years. The widespread use of hollow rope chains and their popularity over the last 20 years has spawned several patents in this area.
The United States is the largest market for rope chains (800 million annually), and hollow rope chains in particular. Price wars have driven the producers to discover new ways of making a genuine gold product with thinner and thinner walls.
With the only criteria being to maximize economic price, poor quality and durability are the general result of making thin hollow gold rope chains. For example, hollow rope chains made of 0.009-0.014 inch diameter wire with a 0.002-0.003 inch wall thickness and having a weight of 1-2 grams/foot represent a significant portion of the U.S. rope chain market. The customer return rate of such hollow rope chains is tremendous. Some of those brittle hollow gold rope chains never reach the retail stores, since the chain is damaged in handling and shipping. Such hollow rope chains have a very short life; the smallest stretch or pressure on the 0.002-0.003 inch wall thickness can damage the fragile hollow rope chains.
Most of the hollow tubing or wire products use copper, steel, plastic or aluminum rod or wires as a temporary installation core at some stage in the manufacturing process. The purpose of such rods or wires is to temporarily support the thin walls of the outer gold tubing or to help coil or form the links of the gold product. These non-precious core materials are disposed of by an acid or caustic soda process at a later stage in manufacturing, resulting in toxic effluent.
Moreover, the hollow gold tubing from which hoop earrings and bangle bracelets are made presents great difficulties in coiling the tube. To prevent the thin hollow gold wall from collapsing, the tube is filled with fine sand prior to the coiling process. Still, damage is common during the coiling process. Due to such problems, a minimum practical wall thickness for this product remains 0.004-0.005 inch.
Background art includes multicolor chains of two different precious metals, such as yellow gold and white gold. The first multicolor chains, which were fashionable about fifteen years ago, were made by a specially developed machine which automatically fed different colored wires alternately to the assembly process. In another process, electroplating the chain with a different colored alloy and diamond cutting the chain to expose the inner alloy produced two-color chains.
U.S. Pat. No. 5,425,228 of Hillel describes a multi-color faceted rope chain and fabrication method. By using metal alloy tubes of different colors, thereby creating overlying layers of different colors in the cross section of the wire, the various layers can be exposed by diamond cutting the chain to different depths. In diamond cutting, a jewelry chain is wrapped around a lathe and cut by a stationary knife held against the edges of the rotating chain. This is a much improved process compared to the plating process for producing multicolor chains. However, Hillel '228, in creating a multicolor chain, makes reference to rope chains made of links produced by wrapping a thin sheet of precious metal around a circular rod wire or core of the second metal of the second color using the same techniques as are now used in producing the hollow links for hollow link rope chain. This method therefore limits the outer layer of the gold sheet to 0.0025 inch or thicker, as noted in Hillel '228.
In the non-precious metal chain costume jewelry market, so called gold filled articles exist, such as noted in U.S. Pat. No. 3,778,238 of Tyler et al for a composite metal article having a superficial gold over layer. However, the interior of the costume jewelry article contains non-precious metals, such as copper alloys.
Furthermore, as noted on pages 5 and 8 of "The Gold Filled Story," a 1982 trade publication of the Gold Filled Association, the making of gold filled articles is an expensive process involving both pressure and heat. To make a gold filled sheet, a layer of karat gold of proper thickness is fused to a suitable supporting copper alloy. Then under pressure and very exacting controls of heat and time, the two metals are fused together so that the bond between gold and supporting metal is flawless and permanent.
With a similar technology, gold filled wire is made by inserting a core of copper alloy into a gold cylinder and then they are fused together under controlled heat and pressure, so that a single round rod is made.
The rod is drawn repeatedly through powerful wire reducing mills and drawing die. This process requires special equipment for the bonding of the two metals together, and heavy rolling mills capable of handling the heavy rod.
In contrast to the gold filled prior art, as it will be disclosed in the Summary and Detailed Description of the present invention herein, by experimenting with silver, it has been found that no heat is required for completing a bonding between the gold and silver, therefore a more shorter technology can be developed for making a two metal wire.
A relatively much thinner tubing than the rod in the gold filled application can be formed while a core of silver wire is being introduced. In this way the starting point of the wire making process is the use of a thicker wire, which can be drawn through drawing dies, and the rolling mill can be avoided as well the heating process.
As defined by the trade definition of a "gold filled" product in the aforementioned 1982 publication of The Gold Filled Association, in order to label a product "gold filled," in the bonding process heat and pressure has to be present, in order to form a permanent bonding between the two metals, namely, gold and the non precious alloy.
Mechanical attachment of a thin layer of gold, such as in a gold filled product, is allowed to be marked as "gold filled," if a layer of at least 10 Karat gold is permanently bonded by heat and pressure to one or more surfaces of supporting metal, thence rolled or drawn to a prescribed thickness.
The Karat gold layer must be at least 1/20th by weight of the total combined gold and base metal.
Other non-precious metal articles are made by electroplating, such as described in U.S. Pat. No. 4,377,448 of Kohl. The electroplating of gold jewelry is a process in which thin layers of gold can be deposited on the surface of a non precious metal by boiling with heat in a caustic chemical bath.
A product can be marked as "electroplated" when at least an equivalent of 7 millionth of an inch of fine gold is deposited on the metal.
In contrast to electroplating, such as in Kohl '448, the present invention proposes to achieve a thin wall product utilizing less expensive procedures than the gold filled process available for the small manufacturer and to create Karat and non Karat jewelry wire or rod products, made only with precious metals such as gold, silver and platinum.
It is safe to assume that in the gold filled process, if the copper alloy is substituted with silver, the process of bonding permanently with controlled heat and pressure silver with gold would be able to produce the wire or rod the present invention has in objective.
However, the present invention does not need such controlled heat and pressure, other than optional annealing at the end of the process, nor does it need the heat and caustic chemical bath of electroplating.
Furthermore, it has not been proposed to utilize a precious metal core with an outer layer of another precious metal, such as gold, in a jewelry rod or wire.
Therefore, the prior art discloses disadvantages and cumbersome heated and pressurized processes for creating thin walled gold filled and electroplated jewelry products. Furthermore, when hollow jewelry products are thus created, the walls are fragile and easily damaged in the finishing processes, such as diamond cutting, or during shipment.